net/netip: document the zero Addr

Fixes #49364

Change-Id: I3372f80723a4deae48ef106f88b0ad880cdd0e45
Reviewed-on: https://go-review.googlesource.com/c/go/+/361914
Trust: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/net/netip/netip.go b/src/net/netip/netip.go
index 1596acbb8ef7ad17bd937a90d8290632d60e1c12..01f6fe5efa086be061414cf256f2ceb736ce2733 100644 (file)
--- a/src/net/netip/netip.go
+++ b/src/net/netip/netip.go
@@ -32,6 +32,9 @@ import (
 //
 // Unlike net.IP or net.IPAddr, Addr is a comparable value
 // type (it supports == and can be a map key) and is immutable.
+//
+// The zero Addr is not a valid IP address.
+// Addr{} is distinct from both 0.0.0.0 and ::.
 type Addr struct {
        // addr is the hi and lo bits of an IPv6 address. If z==z4,
        // hi and lo contain the IPv4-mapped IPv6 address.